Air conditioning



May 7 1940- F. R. mcHowsKY AIR CONDITIONING Original Filed May 26, 1934 QSA INVENTOR.

ATTORNEYS '30 refrigeration.

Patented May 7, 1940 UNITED STATES PATENT ori-ic AIR CONDITIONING Francis R. Bichowsky, Ann Arbor, Mich., assignor to General Motors Corporation, Dayton, Ohio, acorporation of Delaware 6 Claims.

This invention relates to refrigeration, as well as to the heating of air for the purposes of ventilation.

This application is a division of my copending application Serial No. 727,707 flled May 26, 1934. One of the chief reasons restricting the use of equipment for conditioning air for human comfort has been the excessive cost of operation during the summer period. In practical operation, it costs from six to twenty times as much to lower the air one degree of eiective temperature as to heat the air one degree of effective temperature. The reason for this has been that the only known way of lowering the effective temperature any useful amount has been by refrigeration. The cost of refrigeration per unit is much greater than the cost of heating. I have discovered a method of conditioning air in which, under favorable conditions, no artificial refrigeration means is required and in which .cooling mediums, such as water, can be used in their natural temperatures, and which, under unfavorable conditions, requires much less refrigeration than any method known to the prior art, which method is applicable both to cooling the air in summer and heating it in winter. l

In the prior art, the usual mode of' lowering the effective temperature of the air as has been required in summer has been to cool the air by It has sometimes been proposed to use natural cold water to cool the air, but in practice, it is disadvantageous to use cold Water. For if the air is cooled by natural cold water, whose temperature in the summer is usually well above 60 F. such cooling raises the relative humidity of the air to such a point that the air is uncomfortable. Thus air naturally at 80 F. and 50% relative humidity cooled with Water to 60 would have its humidity raised to 97%. It is therefore the usual practice to cool a part of the air to a very low temperature by contacting it with some refrigerating means, thus removing -the sensible heat of the air and by condensation removing a large portion of the contained moisture. Such air is under usual conditions saturated or nearly saturated with moisture 'at the low temperature though its relative humidity may be 100%, its absolute humidity is very low, and by mixing this cool and very dry air with unvtreated. air, it is possible to obtain in the mixture the desired effective temperature. In practice, the method used is to spray a portion of the air Awhich it is desired to condition with refrigerated water, the water being kept at as low a temperature as is practical, usually from 35 to 45 F.

in order to remove as large a fraction of moisture as is possible. With this method, only a certain portion of the moisture can be removed. In practical operation, the resultant treated air seldom has a relative humidity less than to In order to obtain air which has a lower relative humidity, it has been proposed to replace the water by some non-congealing solution such as calcium chloride and sodium chloride solutions, with concentrations below 30 and 25% respectively, the limitations of concentration being xed by the fact that above these concentrations these solutions precipitate solid or freeze at temperatures below 32 degrees F. By the use of such congealing solutions, it is possible to obtain air of almost any degree of dryness, though often such air will be so cold that it must be warmed for comfort and thus it is necessary to re-heat it before use. Other things being equal, the cost of refrigeration is roughly proportional to the number of degrees of cooling required times the amount of heat removed. Either of these means of conditioning air for comfort is therefore expensive.

I have discovered that it is possible to improve the efficiency and greatly lower the cost of air conditioning for comfort by operating according to the process of which the following is in specification: Instead of cooling the air and at the same time removing moisture, I rst treat the air so as to remove moisture and then cool the air. By operating in this manner, I find it is possible to obtain several-advantages.

In the first place, it requires` much less cooling to cool dry air than to cool air containing moisture. 'Ihis is because of the fact that in cooling moist air, it is necessary to remove not only the sensible heat of the air, but the latent heat of the vapor. Operating in accordance with my process, I therefore require less cooling to obtain the same final temperature than would be required to obtain this temperature by any of the means known to prior art.

Secondly, operating according to my process, it is notl necessary to cool the air to as low a temperature in order to obtain the same degree of comfort. It is a known fact that the apparent or effective temperature of air can be lowered by lowering the humidity or by lowering the temperature. For example, air at a relative humidity of 35% which may be easily obtained by my process has the same apparent or effective temperature at as air with '70% relative hu`- CII refrigeration, it is necessary to Contact the air with a liquid drying agent with great drying power. Experiments have shown that both the degree of comfort and amount of cooling necessary for equal effective temperatures depend on the relative humidity of the air. Thus if the air is dried to 5% relative humidity at 90 F. and

cooled to 81 F. which is the required degree of.

cooling for outside temperatures of 95 F. the amount of cooling required is .18 B. t. u. per cubic ft. The resultant relative humidity is 20% Similarly for air at 90 F. and at respectively 25, 35, 45, relative humidity, the amount of cooling to reach comfort is 0.24, 0.28, 0.34, 0.38 B. t. u. per cubic ft. of air, the resultant/humidity is respectively 38, 55, '77, 100% relative humidity. As is well known at any temperature, relative humidities above 55% give a sticky uncomfortable feeling while humidities below 25% feel very dry. The ideal range of humidities before cooling for air dried at temperatures of 90 F, is from 1'7 to 25%. At other temperatures near room temperature the desirable range is about the same. In order that such drying agents may be readily moved from place to place, and in order that they may be easily placed in contact with the air, it is necessary that they be liquid at the concentrations used and over the temperatures met in practice. In order that the moisture which is absorbed by said drying agent may be removed, so that the drying agents may be used over again, it is necessary that they are stable towards heat and not corrosive. I have found that liquid drying agents known to the prior art, such as solutions of calcium chloride, sodium chloride, sulphuric acid and glycerine are undesirable since these solutions either do not have the necessary drying power at room temperature or are corrosive or unstable. I have discovered that there are certain solutions that meet the requirements of my process, namely phosphoric acid; certain acid-anhydrides; certain poly-alcohols, such as ethylene glycol; certain ammonium salts; such as ammonium rhodanate; certain lithium salts, such as lithium chloride or lithium bromide, lithium iodide and lithium rhodanate; and certain calcium salts such as calcium rhodanate. In practice, I prefer to use solutions of lithium chloride, and bromide as disclosed in my copending application Serial No. 457,142. In order to economize, I prefer to use such liquid drying agents at room temperature or slightly above or below and to contact them with air in such a way that the air'leaving the liquid drying agents is at as near the same temperature as the entering drying agent as is possible and is at as low relative humidity as the drying agent will allow; that is to say, I prefer to contact the air and liquid drying agent at as near equilibrium conditions both in respect to temperature and humidity as is possible. In order to keep operating costs as low as possible, I prefer to use the liquid drying agent over-and-over again removing that portion of the moisture which is absorbed by the drying agent or adding that portion of the moisture which was lost by the drying agent, conveniently by evaporating a portion of the drying agent or by adding water to a portion of the drying agent as is desired.

It is one of the advantages of this process of air conditioning that it can be applied in a great number of different ways. For example, it may be used only to condition air in the summer, in accordance with the general process as here before described. or it may be used to condition air in winter as will be more fully described hereafter, or it may be used for both of these purposes. In the process of conditioning air in the Winter, it is, in general, necessary to heat the air and to humidify it. In my general process of air conditioning, as herein described, air is first placed in contact with a liquid agent at essentially equilibrium conditions.A It is an advantage of this system, that, by employing liquid agents of the class described, they have a reversible moisture exchange with the air being conditioned, since they will serve either to dry the air, if the entering air has a relative humidity higher than corresponds to the partial pressure of the Water over the solution, or to moisten the air, if it has .a humidity less than that which corresponds to the partial pressure of the water over the solution. Therefore, by rst `contacting the air with solution of proper strength, it is possible to obtain air at a desired humidity either by removing humidity from the air or by adding humidity as the case may require. In accordance with my process as applied to winter conditions, the air of controlled humidity produced by the rst step in the process is heated to the desired temperature as the second step in the process. It has been found practical to use exactly the same apparatus for heating the air in the winter as may be used for coolingr the air in the summer by substituting hot water, steam or other source of heat in the winter for cold water or other source of cold in the summer.

In the drawing:

Fig. 1 is a diagrammatic representation of an apparatus for practicing my invention; and

Fig. 2 is a diagrammatic representation of a modified form of control which may be used with the apparatus shown in Fig. 1.

An advantage of my process of air conditioning is that it can be applied to existing air conditioning equipment, as well as to novel equipment and novel combination of old equipment.

In the drawing there have been omitted the means for conveying the air, from an enclosure or room Ato and from the device in which it is conditioned. These means will usually consist of ducts and fans, together with such means of regulating the ilow of air and of introducing outside air as is usual with the art. The direction of the flow of air is indicated by parallel arrows and direction of the ow of liquid indicated by single arrows placed along the pipes.

It is to be understood that any of the well known means for automatically or semi-automatically controlling the operation of the various functions may be provided. In particular, the controls may be provided to regulate the density or concentration of the concentrated uld produced in the regenerator. Means may be provided for regulating the temperature ofthe fluid as returned to the sump. Means may be provided for regulating the density or concentration of the uid in the sump. Means may be provided for regulating the temperature of the uid in the sump. Means may be provided for controlling the air flow through the contacting device. Means may he provided for adjusting the portion of external air added to the compartment and to the contacting device. Means may be provided for controlling the temperature of the cooling and heating means. Means may be provided for adjusting various valves. regulating the operation of the system.

It may be desirable to maintain the drying power of the fluid at the sump either at a predetermined constant value or at a value such that the humidity of the space to be conditioned is maintained constant or at a predetermined value. To accomplish this there may be placed in the sump, or connected to it, a densitometer, either of the type shown in Fig. 1 or of the type shown in Fig. 2, the construction and operation of which will be explained more fully hereinafter.

In Fig. 1 is shown a preferred arrangement of the system with operating controls provided as above. -In this iigure |0a is a duct or opening adapted to receive air from the compartment or compartments which are to be conditioned. This air is first passed into the chamber 20a. There is also provided in this mode of operating -my process a second duct |1 through which can be drawn fresh air. The air from the duct |1 enters the chamber 20a where itmay be mixed with the air from the duct |0a. In the chamber 20a' the air from the `combined sources is sprayed with a concentrated liquid solution of my novel drying'agent produced by means of the nozzles 1120. Preferably, the direction of spray and the direction of air ow should be opposite. 'Ihe spray after contacting with the air may be col-P lected in the sump 1100. rIfhe air in the chamber 20a, after having passed through the spray, is heated or cooled by the interchanger 1848. Conveniently, the heating or cooling fluid passing through the pipes of said heat interchanger may be made to flow in a general opposite direction to the direction of air flow. It will be usually convenient to provide a motor-driven fan 1821 in the air duct. It is generally advantageous to place the fan at the point shown since. by this arrangement the sections of the apparatus 20a, etc., which are filled with spray, are under suction instead of under pressure. After leaving the fan 1821, it is convenient to take off the duct a separate ducts 10a and 10aa leading to separate rooms. It is sometimes found convenient to use, during the winter, in connection with or in place of the heating produced at 1848 other sources of heat such as small hot air gas furnaces 183| and 1832.

Returning now to the source of the drying solution, it will be noted that the solution in passing through the spray, if the air has a relative humidity greater than that of the spray, will pick up moisture, and thus dilute the brine supply in the vsump 1100, To maintain this supply at a predetermined concentration, a certain portion is continually or intermittently drawn off by the pump 1103. From hence it is forced through the interchanger 1600 and hence into the boiler 1000. Heat is suppliedto this boiler through the heat source 1020 which maybe a gas burner, oil burner or any source of heat in the boiler whereby a portion of the contained water is boiled off as steam through the pipe 98. The hot concentrated drying agent is drawn oft' through the pipe 1|00 which may be provided with a vent 99| and suction branch 992, through the interchanger 1600 where it serves to heat the portion of drying solution owing through said interchanger and at the same time is cooled thereby. Continuing 'into the lower portion of the interchanger it is further cooled by liquid in the coil 945 and flows from hence via the pipe 92a into the sump 1100, thus maintaining the liquid in said sump at the desired concentration. From the sump 1100 the liquid is drawn off through the pipe 110| by means of the pump 1102. It may be further cooled or heated in the interchanger 11 I0. From this interchanger it is forced through the pipe 11|| into 4the sprays 1120. Water is admitted to the interchanger 1848 through the valve 1845 e from a natural source, or spray tower, or other source of water in or near the natural temperature range 65 to 80 F. The water, after leavingthe coil 1848 ows into the interchanger 11|0 serving to precool the sprayed drying solution. From hence it may ow through the cooling coil 945 and then to waste.

The drying liquid which has been concentrated in the regenerator or rectier y1000 returns via the pipe 1 |00 and a certain portion passes into the branch 1200 which conveys drying liquid to the base of the densitometer chamber 1300. From hence the liquid overows at a constant level out the pipe 1400 and is joined by the main stream of liquid through the pipe 1500 in the intercooler 1800. From whence it returns via the unnumbered channels to the sump 1100. There is provided in the chamber 1300 a float 13|0 provided with a stem 1320 which is constrained to move with the body of the oat as the liquid density changes. 'Ihe vertical motion of the iioat actuates a lever 1330 which makes electrical contact with a contact 1340 thus opening the contact when the density of the fluid in chamber 1300 becomes greater than a predetermined value. An electric circuit 1350 is provided so that on breaking the contact 1340. the valve 10|0 will be closed or restricted, thus decreasing the iiow of fuel to the valve 10|0 through the burner 1020 and thus controlling the flow of heat to the regenerator 1|00, thereby retaining the concentration of the fluid leaving the regenerator 1|00'at a constant predetermined value. In the circuit which circulates fluid from the sump 1100 to the spray nozzles 1120, which circuit consists of a pipe 110|, a pump 1102, the interchanger 11|0, and the pipe 11I| there is provided a Abranch 1130 leading'a portion of the fluid circulating to the base of the densitometer l1140 and from hence by the overflow 1150 back to the sump 1100. l

There is provided a float 1160 with a stem 1165 so arranged that the body of the float is under the liquid level. The float actuates a lever 1110 which makes contact at 1115 with 4a contact 1111, the position ofisaid contact being variable in accordance with the motion of a bellows 1180, said bellows being actuated through the pipe 1185 by the expansion of liquid in a wet thermometric bulb 1190 or actuated by any other device responsive to the relative humidity. The humid bulb thermometer 1190 may be placed in the space to be air conditioned as is desired.

There is provided an electrical circuit 1195 which will be made or broken by the contact of the lever`1110 with the contact 1111 and will thus turn on and off or partially turn on or off, the pump 1103 thus regulating' the amount of liquid flowing through the circuit which includes the pump '|103 and the regenerator or rectier 1000. 'I'he amount of liquid flowing through this circuit will therefore be responsive to changes in density of the liquid flowing through the circuit and will be maintained so as to give a density such that the humidity or wet bulb temperature in the space 1800 is maintained at a desired iigure. There is provided also in the space 1800 av thermostat 18|0 responsive to the temperature of said space and'controlling by means of the electric switch 1820 the gas burner valves 1835 and 1836 and by means of the switch 1825 the operation of the fan 1821 and by means of the switch 1840, the operation of the valve 1845. The valve 1845 may, if desired, be controlled by an outside thermostat 1845a instead. Circulation of air is 75 controlled by the fan 1821. 'I'he amount of heat being supplied is controlled by the gas burners 1832 and 183|, which gas burners will generally be arranged so that they will not be on except when the temperature falls below a predetermined value. The flow of cooling uid through the cooling coil 1808 is controlled by means of the valve 1845.

Inasmuch as it may be desirable to maintain the drying power of the fluid at the sump either at a predetermined constant value or at a value such that the humidity of the space to be conditioned is maintained constant or at a predetermined value, there may be placed in the sump or connected to it a densitometer of the type shown in Fig. 2. In Fig. 2, 1000 is a sump such as has been shown in Fig. 1 connected to which by the pipes 1100, 1200, is a chamber 1300 containing a submerged float 1400 with a stem 1650 operating a movable lever 1500, said lever making contact with one or two contacts 1600, 1650. The condition of these contacts may be made variable so that the concentration which is to be maintained in the sump may be controlled either manually or automatically. For example, the contacts may slide in slots 165i, on an insulated base 1100. The position of the contacts in these slots may be automatically adjusted in accordance with the humidity of the space to be controlled or in accordance with some combination of the temperature and humidity of the space to be controlled by means of the linkages 1109, 11H1, operated by the bellows 1120, 1130, the motion of which is controlled by the temperature or humidity of the space to be conditioned or by some other means.

It may be also desired to control the temperature of the liquid in the sump either to maintain it constant or to maintain it at a predetermined value in accordance with the temperature of the space to be controlled. For this reason a thermostat may be provided, the operation of which will regulate the amount or temperature of the cooling water or other cooling means used to cool the liquid in the sump or flowing to the various contacting units. The amount of air through the various contacting units may be controlled by means varying the speed of the blower or by opening or closing various baiiies, not shown, but which are well known to the art.

Various interconnections and safety devices may be provided, as is known in the art. These devices are not shown in the figure.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow. y

What is claimed is as follows:

1. In an air conditioning system, an air contacting chamber, means for circulating air through said contacting chamber, means for circulating a hygroscopic liquid in contact with air in said air contacting chamber, a sump for said liquid, a concentrator for said liquid, liquid flow connections between said sump and said concentrator, means for circulating a cooling fluid in thermal exchange with air in said air contacting chamber, means for thereafter circulating said cooling uid in thermal exchange with hygroscopic liquid about to contact air in said contact chamber, and means for thereafter circulating said cooling fiuid in thermal exchange with hygroscopic liquid flowing from said concentrator to said sump.

2. In combination, means for drying and cooling air for an enclosure comprising an air contacting chamber, means for circulating a cooling fluid in thermal exchange with air in said chamber, means for circulating hygroscopic liquid in contact with air in said contacting chamber, a sump for said hygroscopic liquid. a concentrator for said hygroscopic liquid, iiow connections between said sump and said concentrator, means whereby concentrated liquid iiowing from said concentrator to 'said sump ows in thermal exchange relationship with liquid flowing from said sump to said concentrator, and thereafter flows in thermal exchange relationship with cooling fluid discharged from said chamber.

3. Control means for a hygroscopic liquid concentrator comprising a first contact member, means responsive to the density of a body of hygroscopic liquid for actuating said rst contact member, a second contact member cooperating with said first contact member, and means responsive to one function of the psychrometric condition of air for actuating said second named contact relative to said rst named contact member.

4. In an air conditioning system', an air contacting chamber, means for circulating air through said contacting chamber, means for circulating a hygroscopic liquid in contact with air in said air contacting chamber, a sump for said liquid, a concentrator for said liquid, liquid ow connections between said sump and said concentrator, means responsive to the degree of concentration of hygroscopic liquid in said sump for controlling the ow of hygroscopic liquid between said sump and said concentrator, and means responsive to the degree of concentration of liquid in said concentrator for controlling the concentration of said liquid in said concentrator.

5. In combination with apparatus for regenerating a hygroscopic mediumfor use in drying a gas, a device for measuring one function of the moisture absorbing ability of said medium, apparatus operated by said device for controlling the regeneration of said medium, and 'humidity responsive means for adjusting the setting of 55 said device.

6. In combination with apparatus for regenerating a hygroscopic medium for use in drying a gas, a device for measuring one function of the moisture absorbing ability of said medium, appa- 00 FRANCIS R. BICHOWSKY. B5 

